1. Field of the Invention
The present invention relates to an improvement in a pad clip device for a disc brake as disclosed by the present applicant in U.S. Pat. No. 4,037,689, assigned to the assignee of the present invention. The pad clip device is disposed between a friction pad backing plate and a backing plate support which slidably guides the friction pads. The pad clip eliminates rattling between the backing plate and the support and is also utilized as a means for producing an audible sound during braking when the lining of the friction pad reaches a predetermined allowable limit of wear. The pad clip of this invention is provided, particularly on the projecting side portion thereof, with a means for limiting the projecting side portion of the pad clip from moving in a direction away from the plane of the disc so as to prevent failure of the warning sound system, while still providing the pad clip, particularly the projecting side portion thereof, with a sufficient resilience to press the disc.
2. Description of the Prior Art
In a disc brake, in general, a support 2 is secured to a stationary part of a vehicle with bolts screwed into holes 1, as illustrated in FIG. 1. Protrudent portions 4a of a backing plate 4b of each friction pad 4 are loosely fitted in right and left guide grooves 3 provided in the support which absorbs the braking force generated on each friction pad. The backing plates 4b are freely slidable in a direction transverse to the plane of a brake disc 5. Two friction pads are disposed on each side of the disc 5 which rotates in the direction indicated by an arrow in FIG. 1. The brake is applied to the wheel through the disc by pressing the friction pads against the disc by means of an acting portion and a reacting portion of a caliper 8.
Since the backing plate 4b of the friction pad 4 loosely engages with the guide grooves 3 of the support through the protrudent portions 4a, the backing plate 4b tends to rattle and produce noises when the wheels of the vehicle vibrate or when a shock results from braking. To prevent such rattling, it has been proposed to insert a resilient metal pad clip 6 between the guide groove 3 and the protrudent portion 4a. With such an arrangement, the rattling of the backing plate of the friction pad 4 can be prevented by the resilience of the pad clip 6.
Applicant's previous invention was directed to producing an audible warning sound by utilization of the pad clip device when the lining of the brake friction pad had worn to a maximum allowable limit. The present invention relates to a pad clip device which provides a means thereon, particularly midway on the projecting side portion of the pad clip to limit a movement in the direction away from the plane of the disc in order to prevent a failure in the warning sound system owing to the projecting side portion of the pad clip being pushed away from the disc by a small protuberance produced by rust, etc. on the surface of the disc or the projecting end, and thus ensures a stable and satisfactory function of the pad clip for producing the warning sound.
As illustrated in FIGS. 2 through 4, the pad clip device 6 of the previous invention takes the form of a long U-shaped arrangement formed from a resilient material, such as metal. A base portion 6a is bent sideways at an angle of 90.degree. to form one side portion 6b and a projecting side portion 6c. The one side portion 6b of the pad clip 6 is provided with a hole. A protrusion 4c in the form of a short stud protrudes from the backing plate 4b of the friction pad 4. The protrusion 4c is inserted through the hole 6e' in the one side portion 6b. After insertion, the protrusion 4c is expanded in the shape of a rivet head to secure the pad clip 6 to the backing plate 4b. The projecting side portion 6c of the pad clip 6 is extended to have the end 6d coincide with the thickness 1 of the lining 7 of the friction pad when the pad has worn to the predetermined allowable limit, and also acts to press the support 2 so that the friction pad 4 is biased in a direction of rotation of a disc 5 (in the direction of the arrow in FIG. 1). With the pad clip 6 arrangement described above, the rattling and noise between the support 2 and the backing plate 4b of the friction pad 4 is prevented by the resilient contact of the projecting end portion of the pad clip 6 with the support 2. In addition, the end 6d of the projecting end portion 6c comes into contact with the disc 5 to produce a warning sound when the lining 7 of the friction pad wears out as shown in FIG. 4.
The arrangement of the pad clip device in the previous patent provides a vibration of the side portion 6c with a sufficient amplitude, but does not provide a sufficiently strong resilience for pressing the end 6d of the pad clip 6 against the disc 5, which results in the end 6d of the pad clip 6 failing to come in contact with the disc 5 even when the lining reaches the limit of wear if there is a small protuberance produced by rust, etc. on the surface of the disc or the end portion 6d. Therefore, the pad clip of this arrangement is unstable in producing a warning sound.